The invention relates to a print head electrode for maximum resolution metal paper printers.
In metal paper printers (electroerosion printers) a metal coated record carrier is printed upon with the aid of an electrode print head. The print head can comprise one or several individually controllable electrodes which are in contact with the metal surface of the record carrier. As one of the electrodes is energized, the metal coating of the record carrier is evaporated at the contact point between the electrode and the record carrier, so generating a visible image element. By suitably controlling the various electrodes and by advancing the print head across the record carrier, text and graphic image information are visibly recorded.
During this process, the resolution of the print image is a function of the image element size which, in turn, is a function of the cross-section dimensions of the print electrode. For high resolution print images the use of very thin electrodes is indispensable. However, the facilities of producing such electrodes are limited.
On the one hand, it is not possible to draw very thin electrodes from a bare electrode wire, and on the other hand it is not possible to produce such print electrodes by etching (cf. also German Offenlegunsschrift OS 21 62 438). Apart from the problems connected with the production of fine print electrodes, the application of such very thin print electrodes is uncertain. Generally, print electrodes are embedded in the supporting material of the print head.
To ensure perfect contact between the electrodes and the record carrier and for wear reasons, the electrodes must protrude from the supporting material of the print head. In the case of very fine electrodes, this requirement could not be met, since even if the electrodes protruded from the supporting material only very slightly, their mechanical buckling or bending strength would be insufficient. Because of this, they would have to be embedded in the supporting material almost to their tips, which would be impracticable because of the high wear encountered.
To counteract the wear problem, it is possible, as previously proposed, to guide thin electrodes of adequate mechanical stability in glass tubes. For feed reasons, however, this solution is unsuitable for extremely thin electrodes because of their insufficient mechanical stability.
Therefore, it is the object of the invention to provide for maximum resolution metal paper printer electrodes whose mechanical stability is such that it permits them to protrude sufficiently from the supporting material of the print head body or to be reliably refed, if and when required.
A further object of this invention is to provide a composite electrode for metal paper printers comprising two materials with differing melting points and wear characteristics for improved mask resolution and electrode life.